Production of cracked gasoline having low gum content



A, P. SACHS Oct. 13, 1936.

2,057,268 PRoDUciTIoN 0F GRAGKED GAsoLINE HAVING Lw GUM- CONTENT `l Filed July 1'?,- 1934 ArfoRNEY Patented Oct. 13, 1936 UNITED STATES lPATENT OFFIQE PRODUCTION OF CRACKED GASOLINE HAVING LOW GUM CONTENT Application July 17, 1934, Serial No. 735,551

3 Claims.

1 My present invention relates to converting heavy hydrocarbon oils into motor fuels of the gasoline type. MoreV especially it relates to the type of process as exemplified in the Beardsley 5 et al.` Patent No. 1,842,318, in which type of process the oil is first vaporized, then preferably superheated, and the superheated vapor mingled with a gaseous heat carrier having suflicient heat units to effect the desired conversion. I have nowV discovered that by suitably regulating the amount and pressure of the heat-carrier gas it is possible to produce a gasoline which is satisfactorily low in gum-forming constituents. My discovery is based on the observation that by the presence of the heat-carrier gas in suitable quantity, it is possible to insure that at an appropriate point in the system the gasoline component shall be in vapor state while the gum-forming substances will, on the other hand tend to remain in liquid state and thus be at least partially separated from the gasoline substance. More specifically, the conditions which I have found to insure this result are that sufficient gas say of specific gravity of .'7 air: 1.0) be present so as to enable the gasoline to exist in the vapor state at a temperature at least approximately 100 F. below the boiling point of the gasoline under standard atmospheric conditions. In this manner, the gum-forming substances will be retained in the so-called rectier bottoms in larger proportion than under normal conditions while the gasoline vapor is condensed in the gasoline condensers.

My invention will be best understood by reference to the following detailed description taken with the annexed drawing which shows diagrammatically an outline of a plant suitable for carrying out my invention.

Referring to said drawing, oil to be converted from the supply tank I0 may, through pipe II,

be introduced into a scrubber I2 to be described hereinafter. Conditions are maintained in the scrubber so as to vaporize from the charging stock all components which are to be subjected to cracking as overhead distillate which passes out through pipe I3 by which it is fed to the rectier I4 where special conditions are maintained, to be hereinafter described. For the moment it is sufficient to say that the oil to be cracked is condensed in the rectifier and is removed therefrom by pipe I6, by means of which it passes `to a vaporizer I1, flash drum I8, and superheater I9, wherein the vapor is heated to say from 850 to 950 F. The vapor now passes from the superheater to the reaction chamber 20 by means of pipe 2I. In the reaction chamber 20 the vapor is mingled with hot gas which has been generated in one of a battery of ho-t blast stoves 22 and introduced into said reaction chamber through pipe 23. The cracking reac- 5 tion occurs in the chamber 20 and the mixture of cracked products leaves said chamber through pipe 24, passing to the scrubber I2 already mentioned. Here the products lose a portion of their heat, and due to the scrubbing action, any 10 particles of free carbon or tarry matter which may have been carried along. The hot scrubbing oil is removed through pipe 25 and circulated to various points of the system whereat it delivers up its heat, as for example in the 15 manner described in the patent to Beardsley No. 1,883,744. The overhead products including the original heat-carrier gas and the vapors of the cracked products now are subjectedto rectifying conditions in the rectifier I4. I-Iere conditions 20 are so maintained that the gasoline, if liquid, would be vaporized at a temperature approximately of below its normal atmospheric boiling point. To bring about these conditions, I preferably employ an amount of gas which is at 2 least equal in weight to the gasoline vapors which are to be subjected to rectification at a system pressure of say fifty pounds above atmospheric. Under these conditions the gumforming constituents tend to remain as liquid in 30 the rectifier I4, although they are not completely removed. A portion of the liquid in the rectifier I4 may be withdrawn, cooled in the cooler 26, and reintroduced into the rectifier through the pipe 2l in accordance with known 35 practice, or, preferably, some of the gasoline condensed may be used as reflux by means of connections not shown. At the same time, a portion of the oil containing the bottoms is removed from the cooler through the pipe 28. 40

In order to provide for greater flexibility and to insure proper conditions in the rectifier, I provide an auxiliary gas supply either to the rectier or to the scrubber. As shown, a portion of the gas in pipe 40 (through which is 45 passed stripped residual gas of the system, as will be described) may be passed through a heater 30 which may be suitably heated by waste heat in the system from a source not shown, thence through pipe 3| having a branch 32 to 50 the rectifier I4, a branch 33 to the scrubber I2. The temperature to which the gas is heated would preferably be on the order of say 500 F. so as not to` unduly disturb the temperature equilibrium in either the rectier or scrubber. 55

In this manner should it be desired to operate in the cracking zone With less gas constituting the heat carrier proper than Would be required by conditions in the rectier, such deficiency may be made up by such auxiliary supply.

There now remains merely to separate the gasoline vapor from the heat-carrier gas for which purpose I employ the condenser communicating With an accumulator 36. From the accumulator 36 the gas and residual quantities of gasoline escaping condensation in condenser 35 pass through an absorber 31 to take out such residual gasoline, after which a portion of the gas may be fed to the gas holder 39 While a suitable portion is returned to the hot blast stoves through the pipe 4U, there to be heated and to recommence the cycle.

I claim:

1. In the process of converting hydrocarbon oil into motor fuels of the gasoline type which process employs a conversion temperature in excess of 950 degrees F. and in which conversion is brought about in the vapor phase by the aid of a heated substantially inert heat carrier gas which is mingled with the Vapor of the hydrocarbon undergoing conversion, the mixture of the conversion products submitted to rectication in which the products heavier than the gasoline component are condensed out While leaving said gasoline component in Vapor form, the improvement which consists in regulating the amount of gas present during rectification by adding gas at a point subsequent to the reaction chamber so as to insure that sufficient gas, in excess of equal parts by Weight of gas to gasoline vapor, is present as will exert sufficient partial pressure effect upon the gasoline vapors as would enable said gasoline, if a liquid, to be vaporized at at least degrees: F. below its atmospheric end boiling point whereby gum forming substances formed in the conversion reaction are in large part retained by the condensate, and then separating the gasoline from the gas present by liquefaction of the gasoline.

2. The process according to claim l, in which the pressure of gas in the rectier is approximately fty pounds to seventy-five pounds per square inch.

3. The process according to claim l in which the gas is that which is produced in the oil conversion step.

ALBERT P. SACHS. 

